Weaning from mechanical ventilatory support is the process of assisting patients to breathe spontaneously without mechanical ventilation. Despite the development of advanced ventilator technology and the growing literature on weaning, the most advantageous approaches to weaning remain to be determined. The purpose of this study is to test a model of weaning by determining the pattern of physiologic stability, the readiness threshold for weaning and the patterns of ventilator support and weaning progress. Methods: A pilot study in 10 subjects will be conducted. Each subject will be followed from time of intubation until a weaning outcome is reached. The revised Burns Wean Assessment Program will be assessed every day to determine the readiness threshold and the pattern of physiologic stability. The weaning process chart will be completed twice daily to assess the patterns of ventilator support and weaning progress. Receiver operating characteristic curves will be used to determine the readiness threshold. Growth curves will be used to determine patterns in ventilatory support and weaning progress. Summary of Findings: Data collection continues.